Hatz Biplane Association

Jackal wrote:I researched on google the 302/304 difference and it seems you have to be a metallurgist to understand the difference, but it seemed to me the difference was minimal, and the firewall is arguably not structural anyway.

-Jackal

I am a metallurgical engineer , the difference for this application is pretty minor. 304 is going to have a bit more corrosion resistance by virtue of lower carbon content and slightly higher chrome content compared to 302. It's enough of a difference that if I were to be given the choice of 302 or 304, I'd pick 304 (even if it cost 10% more), but not enough that I wouldn't lose sleep over it if all I could get was 302.

Dustin

I went to the hangar yesterday and did some measuring. The numbers I posted earlier must be gauge numbers. The old firewall measured .030" and the new firewall measures .040".

Sorry for any confusion.........

J/C GTF

Good thinking guys. Thanks for the advice.

Nick

Try sheet metal -fabrication, suppliers, till you get a lead on one that does restaurants, commercial kitchens, etc---nearly all that work is done in SS.In Okla City, there are 2 or 3 metal salvage yards (junk yards) that keep usable remnants of structural steel, Stainless, copper, etc in separate areas of their buildings.. Jerry

The firewall in Hatz #3 was stainless that if I remember right was .018". It was warped and distorted, looked like hell especially around the four motor mount attach points. I replaced it with the next size up, .020", again if I remember right.

There is no need to buy this stuff from aircraft supply stores. I went to the local steel supply and bought the stainless plate. Got a deal on a remnant that is polished on one side! Good luck bending the top radius........ only .002" thicker makes it seem twice as strong! I had an idea to bend it but could not find the proper tool..........

J/C GTF

For what its worth, I'm building a cb-1 and plans call for .016 grade 302 ss. Wicks aircraft supply (who has done a great job for me over 18 years and 4 aircraft) carries only one ss material which is .018 grade 304. I used that. I researched on google the 302/304 difference and it seems you have to be a metallurgist to understand the difference, but it seemed to me the difference was minimal, and the firewall is arguably not structural anyway. I once built a formula one racer which called for a firewall of either stainless or galvanized, at builders preference. I'm sure there was more difference in these materials than in 302 vs. 304. So there you go for what its worth. Be advised I am a tinkerer with no credentials.

-Jackal

Good Evening Hatzers!

What material did you use for your firewall? Plans call for .024 stainless, but I don't see that available on ACS&S.

Help appreciated.

Nick